Priority is claimed to Patent Application Number 2001-43504 filed in Republic of Korea on Jul. 19, 2001, herein incorporated by reference.
1. Field of the Invention
The present invention relates to a microcooling device, and more particularly, to a microcooling device having a microchannel array which allows a coolant to flow into a heat generator by a capillary force.
2. Description of the Related Art
General semiconductor devices have several volts of operating voltages. However, a semiconductor device does not utilize the whole of electric energy being supplied, but discharges a portion of the electric energy in the form of heat because of resistances of materials of several components constituting the semiconductor device.
Heat may sharply deteriorate the performance of a semiconductor device and damage the semiconductor so that the semiconductor itself or important parts constituting the semiconductor device are not restored if serious. Thus, one of elements of prolonging reliability and lifespan of an electronic device is to effectively remove heat inevitably generated during its operation.
Various cooling devices are adopted to remove heat generated in chips or electronic devices. For example, in a case of a computer, an air-cooling device, which flows external air thereinto, circulates it around, and cools it using a fan, is generally used to remove heat generated from built-in semiconductor chips. A water-cooling method is more preferable than an air-cooling method in consideration of cooling efficiency of coolant. However, in the water-cooling method, a short circuit may occur due to a water leakage and an additional device such as a condenser or the like, is necessary. Thus, the water-cooling method is limitedly used.
Nevertheless, as the amount of heat generation increases in an electronic device, an attempt to cool the electronic device by the water-cooling method has bee made because of cooling limitation of the air-cooling method. In particular, chip unit cooling has been attempted. However, heat (heat fluid) per unit area generated in a chip region is almost equal to heat fluid per unit area generated in a rocket engine. Thus, microcooling devices using microchannels with high heat conductivity for effective circulation and phase shift have been manufactured to reduce heat generated in the chip region.
FIG. 1 is a perspective view of a microchannel included in a heat exchanger according to the prior art (U.S. Pat. No. 5,727,618). Referring to FIG. 1, Reference numeral 25 is copper sheets. A solid sheet 60 is placed on the copper sheets 25. The upper surface of the solid sheet 60 contacts a heat generator (not shown). Thus, heat of the heat generator is transmitted to the copper sheets 25 through the solid sheet 60. The copper sheets 25 have been etched with rows of holes 40 that pierce the sheets. The copper sheets 25 have been coated with a thin layer of sliver (not shown), aligned and fused together so that the aligned holes 40 form an array of microchannels 165.
A manifold section 170 formed from a stack of etched copper plates is juxtaposed to the first section with the stack of the copper sheets 25. A first copper plate 65 of the manifold 170 adjoining the microchannel array 165 has a plurality of elongated apertures 70 oriented transversely to and in fluid communication with the microchannels 165. A shaft 135 containing coaxial inlet and outlet conduits 180 and 190 provides fluid to and receives fluid from the manifold stack 170. The series of plates of the manifold 170 form apertures which transform fluid flow from the single inlet conduit 180 to alternately spaced elongated inlet apertures 72 of plates 65, and transform fluid flow back from other alternatively spaced elongated outlet apertures 73 of plate 65 to the single outlet conduit 190.
The single shaft 135 having coaxial inlet and outlet conduits plugs into a modular hole in a case having a fluid supply and drain and a plurality of such holes for fitting a plurality of such shafts. The alternatively spaced inlet apertures 72 and outlet apertures 73 adjoining the microchannel array 165 lower the pressure required to cause fluid to flow through the microchannel 165. The microchannels 165 are formed in a very thermally conductive substrate of copper with small dimensions and large height-to-width aspect ratios.
As described above, the microchannel of the heat exchanger according to the prior art provides fluid which has flowed into through the inlet conduit 180 to the solid sheet 60 adjoining the heat generator through the elongated inlet apertures 72 formed in the manifold 170 and the holes 40 formed in the copper sheets 25, and discharges fluid which has absorbed heat of the heat generator via the outlet conduit 190 through the holes 40 and the outlet apertures 73.
In cooling using such a compulsorily circulating method, the inlet and outlet apertures 72 and 73 adjoining the microchannel array 165 drops pressure. Thus, an additional high-pressure tank or pump is necessary to circulate fluid by overcoming the drop in pressure. Also, microchannels are fouled by dust, other impurities, or the like.
To solve the above-described problems, it is an object of the present invention to provide a microcooling device which can be made small and thin with excellent cooling efficient and a simple structure, does not require an additional device for circulating coolant, and reduce the unit cost of a microchannel array.
Accordingly, to achieve the above object, there is provided a microcooling device including a substrate, a microchannel array, and a condenser. A predetermined region of a lower surface of the substrate contacts a heat source. The microchannel array is placed on the substrate so that a coolant concentrating portion is opposite to the predetermined region of the lower surface. The condenser fixes the microchannel array, condenses vapor generated in a process of cooling the heat source, and allows the condensed vapor to flow into the microchannel array.
Here, the microchannel array includes at least one unit where a capillary force for allowing the coolant to flow into the coolant concentrating portion is generated. The microchannel array includes at least two or more units, any one of which has the same shape as or different shape from the other ones.
The unit includes a frame and a plurality of pins which are connected to the frame so as to be oriented toward the coolant concentrating portion. Here, portions of the plurality of pins are shorter than the others, and distances between the pins are narrow enough to generate capillary forces, preferably, get narrower as being oriented toward the coolant concentrating portion. However, the distances between the pins may be uniform. Also, it is preferable that the pins are linear, but may be non-linear.
The condenser includes a cap and a heat sink. The cap covers the microchannel array and is hermetically sealed at the edge of the substrate around the cap, and the inside thereof contacts the vapor so as to absorb latent heat of the vapor. The heat sink is placed on the cap and absorbs heat transmitted to the cap so as to maintain a temperature of the cap to a predetermined temperature enough to condense the vapor.
Using a microcooling device according to the present invention, a coolant can naturally be circulated without pumping equipment. Thus, since the configuration of the microcooling device is simple and components of the microcooling device are flat plates, it is possible to make the microcooling device small and thin. Also, since it is simple to manufacture units constituting a microchannel array, unit costs can be reduced. Further, it is possible to stack the units so as to have a very wide surface area. Thus, the maximum heat transfer efficiency can be increased.